---
title: "What are the differences between a HashMap and a Hash table in c#?"  
description: "What are the differences between a HashMap and a Hash table in c#?"  
author: "Revati S Misra"  
published: 2023-08-18  
updated: 2023-08-19  
canonical: https://www.mindstick.com/forum/159584/what-are-the-differences-between-a-hashmap-and-a-hash-table-in-c-sharp  
category: "c#"  
tags: ["c#", "java", "hashtable"]  
reading_time: 2 minutes  

---

# What are the differences between a HashMap and a Hash table in c#?

What are the [differences](https://www.mindstick.com/articles/12918/cat-5e-vs-cat-6a-understanding-the-major-differences) between a [HashMap](https://www.mindstick.com/forum/159211/what-are-the-differences-between-a-hashmap-and-a-hashtable-in-java) and a [Hash table](https://www.mindstick.com/interview/23440/what-is-hash-table) in [Java](https://www.mindstick.com/articles/12214/web-development-company-in-india-laid-on-the-foundation-of-concrete-java-programming)?

## Replies

### Reply by Aryan Kumar

The main differences between a hashmap and a hashtable in C# are:

- **Synchronization:** A hashmap is not synchronized, while a hashtable is synchronized. This means that a hashmap can be accessed by multiple threads at the same time, while a hashtable can only be accessed by one thread at a time.
- **Null values:** A hashmap allows null values for both keys and values, while a hashtable does not allow null values for keys.
- **Performance:** A hashmap is generally faster than a hashtable, but it can also be less memory efficient.

Here is a [table](https://www.mindstick.com/articles/43918/how-to-design-table-using-bootstrap) summarizing the differences between hashmaps and hashtables in C#:

| Feature | HashMap | Hashtable |
| --- | --- | --- |
| Synchronization | Not synchronized | Synchronized |
| Null values | Allows null values for keys and values | Does not allow null values for keys |
| Performance | Generally faster | Generally slower |
| Memory efficiency | Less memory efficient | More memory efficient |

The best choice for you will depend on your specific needs. If you need a collection that can be accessed by multiple threads at the same time, then you should use a hashtable. If you do not need synchronization, then you can use a hashmap, which will be faster and less memory-intensive.

Here are some additional things to keep in mind when choosing between a hashmap and a hashtable:

- If you are using a hashmap in a multithreaded application, you should be careful to avoid race conditions. This can be done by using the `lock` keyword to synchronize access to the hashmap.
- If you are storing large objects in a hashmap, you should be aware that the hashmap will need to allocate memory for each object. This can lead to memory fragmentation, which can affect performance.


---

Original Source: https://www.mindstick.com/forum/159584/what-are-the-differences-between-a-hashmap-and-a-hash-table-in-c-sharp

Copyright © MindStick Software Pvt. Ltd. This Markdown version is provided for developers, AI systems, and offline reading.